Dieting? Leptin Levels Affect Diet Response

When dieting and your leptin levels go down, you may find you are more hungry. Researchers found that during the first week of the weight-loss diet, volunteers’ leptin levels dropped by an average of 54 percent.

This is accouding to Agricultural Research Service (ARS) researchers in Davis, California, who are studying the effects of the hormone leptin.

Their investigation at the ARS Western Human Nutrition Research Center is among the first long-term analyses of blood leptin levels in women who are on a weight loss regimen.

ARS chemist Nancy L. Keim led the study. Keim hopes that the leptin findings will “help obesity researchers and others who are trying to determine whether leptin can be used effectively to help people lose weight.”

Twelve overweight but otherwise healthy women, age 20 to 40, volunteered for Keim’s 15-week study. For the first 3 weeks, the volunteers ate a stabilization diet, which determined how many calories they could consume every day without either gaining or losing weight.

For the remaining 12 weeks, the women went on a low-fat, weight-loss regimen. Each volunteer ate 500 fewer calories per day than she would have needed to maintain her starting weight.

Calories derived from fat never exceeded 22 percent of each day’s total calories.

The weight-loss phase of the study also included a program of moderate exercise—walking, weight training, and working out on an exercise bike or treadmill.

Keim found that during the first week of the weight-loss diet, volunteers’ plasma leptin levels dropped by an average of 54 percent. Leptin levels remained low throughout the rest of the study.

What’s more, the incidence of hunger, and the desire to eat, doubled in response to the reducing diet. Says Keim, “The volunteers who reported the greatest increase in hunger and desire to eat, and biggest prospective estimates of how much they’d like to eat at the next meal, were those with the largest drop in leptin.”

Once every 2 weeks, volunteers ranked their hunger by filling out a one-page questionnaire several times during the day. Below each question was a short horizontal line that served as a scale.

To answer the question, “How hungry do you feel right now?” volunteers put a small vertical tick mark toward the left end of the scale if they were “not at all hungry” or toward the far right if they were “extremely hungry.”

“This scale is subjective, of course,” Keim admits, “but it’s really the only way we have right now to assess appetite.”

To get a better idea of how to use the questionnaire and estimate their hunger, volunteers began working with the form during the stabilization-diet portion of the study.

Volunteers with higher leptin concentrations and smaller decreases in leptin were less hungry while on the reducing diet. Decreases in body weight and body fat didn’t seem to play a role in the degree of hunger that the volunteers reported.

Keim collaborated in the study with Peter J. Havel and Judith S. Stern of the Department of Nutrition at the University of California at Davis. The work was funded by ARS, the National Institutes of Health, and the Juvenile Diabetes Foundation, International.

The research is of interest to the diabetes foundation because new information about the relationships among leptin, insulin, and obesity may lead to better ways to prevent or treat diabetes.

The scientists published their findings in the American Journal of Clinical Nutrition.

Marcia Wood, Agricultural Research Service Information Staff, Agricultural Research Service.

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